Firstly you will need to download and apply the denissoliveira variant pack mod https://www.digitalcombatsimulator.com/en/files/3339262/

Then I highly recommend this mod is applied with a mod applying tool like OVGME, otherwise it defeats the objective of being able to quickly apply the different nose colours to match varying skins.

The Mod contains 5 nose mods, individually coloured to match existing British variant skins available in the downloads section, (I take absolutely no credit for these brilliant skins made by our DCS community).

I have edited Deniss,s mod for my own use and after contacting him he has given me permission to share this with the community.
If you want to fly as close to a British variant of the harrier as possible in DCS I cannot praise his work enough it is brilliant.

Place each Nose mod into your OVGME mods folder or similar.

They are listed as :
Harrier Nose colour light Grey
Harrier Nose colour medium Grey
Harrier Nose colour Dark Grey
Harrier Nose colour Desert Pink
Harrier Nose colour Green

you will have to activate your desired nose colour prior to each time you load DCS.

alternatively you can apply the mod individually to coremods/aircraft/AV8BNA/1ModsConfig/textures/ and overwrite the existing GR9_harrier file.
(Again I would recommend OVGME).

This is only for the GR7/9 versions of his Mod,

Hope you enjoy...